Cigarette making machines of the continuous rod type generally involve the showering of tobacco particles in a relatively wide and thin chute in which the particles move vertically upwardly or vertically downwardly onto a belt which moves transverse to direction of movement of the tobacco particles in the chute, resulting in the collection of the tobacco particles on the belt as a tobacco filler rod of narrow width and of increasing depth across the width of the chute in the direction of movement of the belt. Vacuum usually is applied to the surface of the belt opposite to that on which the rod is formed in order to grip the filler rod to the belt by suction.
Following formation of the rod, which usually has a variable weight of tobacco along its length caused by a variety of factors, the rod is trimmed in order to improve the uniformity of the rod weight along the length and then is compressed to a uniform diameter prior to wrapping in paper to form a continuous cigarette rod from which cigarettes are cut. In order to provide a consistent product, it is preferred that the filler rod be as uniform as possible immediately prior to wrapping in paper.
The prior art procedures suffer from a number of drawbacks which result in unsatisfactory cigarettes and uneconomic use of tobacco. One significant drawback results from the manner of formation and conveying of the filler rod from its formation to the wrapping station. The filler rod typically is formed on and is conveyed on a substantially flat moving belt through which suction is applied and which runs in a channel between opposed stationary sidewalls which confine the rod laterally. There is therefore, frictional contact between the sidewalls and the filler rod both during its formation and conveying. Variations in the coefficient of friction between the tobacco and the sidewalls, resulting from variations in the tobacco and/or variations in the sidewalls themselves, for example, due to irregular tar build up, may lead to dislodgment of tobacco particles from the body of the rod or movement of tobacco particles to different longitudinal positions in the rod, resulting in a worsened uniformity of tobacco along its length, leading to large numbers of cigarette rejects, and, under extreme conditions, the machine may become clogged, in which event, production would have to cease until the clog is removed. Therefore, these prior art machine constructions have defects which adversely affect the quality of the product and the runability of the machine.
Further, in conventional cigarette-making procedures, the initially-formed filler rod of relatively wide width is manipulated to decrease its width during passage from the chute to the commencement of the wrapping procedure so that the rod has the desired width for feed to the wrapping procedure. This manipulation, due to the frictional contact between the constraining walls and the tobacco in the rod may increase the above-mentioned problems. Heretofore it has not been considered possible to form a filler rod having the width required for feed to the wrapping procedure, typically less than about 10 mm, particularly about 5 to about 10 mm, due to problems in control of the formation of the filler rod directly from the relatively wide tobacco stream on a thin width surface at high speeds of formation of filler rods, typically above about 4,000 cigarettes per minute, even with the application of suction to the underside of the rod-forming belt. The control problems arise from the increasing thickness of the filler rod on the surface across the width of the relatively wide stream and the decreasing influence of suction with increasing depth. Hence, the prior art necessity to form an overwide filler rod which later is compressed laterally to decrease its width to a size suitable for feed to the wrapping procedure.